Threaded studs are used very extensively in the aerospace field. The stud is secured to a workpiece by a threaded first end threaded into a threaded aperture in the workpiece. A threaded second end protrudes from a surface of the workpiece wherein the second end is used to secure another part to the workpiece.
It is often necessary to remove the studs from the workpiece. For example, the turbine rear frame of the CF6-80C2 and CF6-80E engines have multiple key ring stud assemblies installed on the aft flange hub. The studs may need to be removed when a heat treatment operation is performed on the turbine rear frame. Similarly, these studs may need to be removed if an unserviceable condition is found on a stud during an inspection process.
One method of removing studs from a turbine rear frame is set forth in FIG. 1. As shown therein, a portion of the stud may be cut off slightly above the surface of the hub. A machine is then set up to drill to a depth lower than the bottom of the key ring portion. A second drilling operation is then employed using a smaller sized drill to drill through the bottom the stud or to another depth suitable for application of a subsequent screw extractor. Thus, drilling is conducted through the stud using a drill sized for the particular screw extractor employed. Next, a prying tool is employed to reach under the key ring portion and remove this locking mechanism. The screw extractor with a tapered diameter then removes the remaining inner stud, as shown in FIG. 1.
Although the above method is effective, care must be taken so as not to drill into the parent material of the component. Similarly, there is a risk of damaging the threaded aperture of the component because of the use of multiple drilling operations. This method also involves multiple repair operations and equipment set up procedures and thus often demands many labor hours to complete the removal process.
Accordingly, there exists a need for a method of efficiently removing studs from gas turbine engine components, particularly key ring stud assemblies of a turbine rear frame, without damaging the underlying threaded apertures. The present invention satisfies this need.